Die cutting has always been a very important process in the semiconductor industry. After subjecting to complex fabrication processes, a semiconductor wafer needs to be split into a plurality of small dies or chips by a die cutting process. During the die cutting process, it is desirable not to destroy chip functions and to provide a high production yield. In addition, a too-slow cutting rate may increase cost in the semiconductor chip manufacturing process.
Conventionally cutting blades are used to mechanically cut a semiconductor wafer into separate chips. However such cutting process may apply a large mechanical stress to the wafer. In addition, chips usually have a multilayer structure and stress may be present between various material layers. When subjected to mechanical cutting, the interlayer stress may be released to cause the de-lamination and/or cracking between the material layers along the scribe line between the chips. Further, in the conventional semiconductor chip manufacturing process, a low K dielectric material is typically used for the interlayer dielectric layers to reduce the RC delay of the chip operation. But the low K dielectric material itself is a low density, fragile material. During the blade cutting process, the cutting stress is likely to break the low K dielectric material layers. These issues may reduce the production yield of the cut chips.
Alternatively and conventionally, prior to the blade cutting, a laser cutting process may be performed to pre-cut the wafer to disconnect the material layers between individual chips. Then the blade cutting is performed to completely separate the chips. Compared to the direct blade cutting, using laser cutting to pre-cut the wafer reduces the problems of de-lamination and cracking to certain degree. Nevertheless, due to the intense energy of the laser cutting, the above issues cannot be completely eliminated. Moreover, the high cost of laser cutting does not help reduce the chip manufacturing cost.
It is desirable to improve production yield of dies based on the blade cutting process.